at a rally last night in denver, romney previewed one of his lines of attack. >> we had 43-straight weeks of unemployment above 8%. and what does the president say to all this? he says forward. i think forewarned a better term. >> reporter: romney's trailing president obama in polls. and his campaign knows the upcoming debates could be their best chance to turn things around. that's why the candidate has spent many hours practicing. he'll huddle again with advise herbs practicing today. in the mock debates, senator rob portman is playing barack obama. >> he's playing president obama in the mock debates we have. i don't like him very much anymore. >> reporter: as for president obama, he took a break from practice yesterday to visit a campaign office and make a few calls to unsuspecting voters. >> andrea? hi. this is barack obama. how are you? that's right. >> reporter: it was just a brief break for the president, who, like romney, has been rehearsing for days. senator john kerry is playing the role of romney in president obama's practice sessions. the campaign is managing expectations, say